1. Field of the Invention
The present invention relates generally to the field of high speed data transfer, and more specifically to transparent GFP (Generic Framing Procedure) operation over specific interfaces.
2. Description of the Related Art
Data communication networks receive and transmit ever increasing amounts of data. Data is transmitted from an originator or requester through a network to a destination, such as a router, switching platform, other network, or application. Along this path may be multiple transfer points, such as hardware routers, that receive data typically in the form of packets or data frames. At each transfer point data must be routed to the next point in the network in a rapid and efficient manner.
Data transmission over fiber optics networks may conform to the SONET and/or SDH standards. SONET and SDH are a set of related standards for synchronous data transmission over fiber optic networks. SONET is short for Synchronous Optical NETwork and SDH is an acronym for Synchronous Digital Hierarchy. SONET is the United States version of the standard published by the American National Standards Institute (ANSI). SDH is the international version of the standard published by the International Telecommunications Union (ITU). As used herein, the SONET/SDH concepts are more fully detailed in various ANSI and ITU standards, including but not limited to the discussion of concatenated payloads, ITU-T G.707 2000, T1.105-2001 (draft), and T1.105.02-1995.
SONET/SDH may employ transparent GFP (Generic Framing Procedure) that seeks to overcome issues with transporting data over existing ATM and POS protocols. Transparent GFP, or GFP-T, mapping may be implemented in a device including client stream interfaces and transport interfaces, such as SONET/SDH. Such an implementation is shown in FIG. 1A. From FIG. 1A, the transport interface provides information to and receives information from the optional SONET/SDH or OTN block 51, which in turn interfaces with GFP framing block 52. GFP framing block 52 interfaces with GFP-T adaptation block 53, which provides and receives data over the stream interface. The framer device 50 houses these three components.
If GFP-T carries a Gigabit Ethernet stream (GbE) over a transport layer such as SONET/SDH or OTN, then either a serial GbE interface or a ten bit interface (TBI) or reduced ten bit interface (RTBI) may be needed on the framer device 50. Generally, the GFP-T standard may be adapted by processing GFP-T mapping using two devices connected via a stream interface, or using out-of-band signals. Such a stream interface may be highly dependent on the traffic type mapped.
For a single device that supports GFP-T mapping, the frame-mapped GFP (GFP-F) can also be implemented in the same device. GFP-F mapping protocols including header and HEC (Header Error Check) processing, frame delineation, scrambling, FCS calculation, client management frame insertion and extraction are common to GFP-T and GFP-F mappings. Additional support required for GFP-F in addition to that supported in GFP-T tends to be minimal.
However, in the presence of only stream interfaces, GFP-F can only be used to map packets recovered from the implemented stream interfaces. GFP-F can be used to map any type of packet, somewhat limiting the flexibility of GFP-F mapping.
Two main processes exist in the GFP-T mapping procedure. The first process, called GFP-T Adaptation here, adapts 8B/10B client signals via 64B/65B block codes and adapts 64B/65B code blocks into a GFP frame without the GFP headers. Adaptation also occurs in the reverse direction. The second process is GFP Framing. While GFP-T Adaptation is unique to GFP-T and is also unique for each traffic type, GFP Framing is identical for GFP-T (all traffic types) and GFP-F. Implementing GFP-T in one device (or via a proprietary stream interface) requires adding a new traffic type, such as Fibre Channel, having a different protocol or different rate. In such a situation, a new function may be need to be added.
In essence, advantages may be realized when providing both GFP-T and GFP-F mappings, but implementing them both on a single device can provide certain drawbacks. The difficulty becomes providing a design that captures the benefits of combined GFP-T and GFP-F mapping while minimizing the processing problems noted above.
With these restrictions on implementing GFP-F adaptation and GFP framing, it can be very difficult to realize an effective design where the protocol operates efficiently in the presence of a split design.
A transparent GFP mapping that enables efficient implementation of GFP-F adaptation and GFP framing may provide increased throughput and other advantageous qualities over previously known designs, including designs employing SONET/SDH architectures.